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Sterane and triterpane biomarkers in the Precambrian Nonesuch Formation, North American Midcontinent Rift
Abstract
Molecular fossils and organic matter from microbial communities living around 1.1 Ga ago are well preserved in the Nonesuch Formation of the US Midcontinent Rift System. Although some compound classes of biological markers have been recognized repeatedly in previous studies of Nonesuch rocks and associated petroleums, steranes and triterpanes have not been detected. Failure to detect these compounds was due primarily to instrumental limitations and the relatively high thermal maturity of samples collected within zones of copper mineralization. The authors analyses of Nonesuch samples from the White Pine Mine and nonmineralized localities in Michigan and Wisconsin reveal suites of Cââ-Cââ steranes and Cââ-Cââ pentacyclic triterpanes similar to those found in Phanerozolic oils and sedimentary rocks of marine origin. Stereoisomeric distributions in the Nonesuch samples are consistent with moderate thermal maturity except in the mineralized zone near White Pine.
... High yields of bitumen extracts and biomarker hydrocarbons can be recovered from many Proterozoic rocks (e.g. Summons et al., 1988a,b;Summons and Walter, 1990;Pratt et al., 1991;Logan et al., 1995Logan et al., , 1997Peng et al., 1998;Höld et al., 1999;Li et al., 2003;Olcott et al., 2005;McKirdy et al., 2006;Grosjean et al., 2009;Love et al., 2009). Some characteristic molecular features can broadly distinguish many Proterozoic alkane profiles from those obtained from Phanerozoic-age rocks and oils, such as (1) a higher ratio of monomethyl branched alkanes relative to the dominant n-alkanes and (2) often a more prominent unresolved complex mixture of diverse branched and cyclic alkanes (Summons and Walter, 1990). ...
... These compositional differences are often attributed to a higher input of bacteria over eukaryotes in the Proterozoic, which is supported by generally higher ratios of hopanes/steranes in Paleo-and Mesoproterozoic rocks (e.g. Pratt et al., 1991;Dutkiewicz et al., 2003;Li et al., 2003;. ...
... In the Phanerozoic, dinosteranes are particularly abundant in marine rocks and oils of Triassic age and younger , tracking a later radiation of dinoflagellates, but these same structures are also found in Proterozoic strata as old as ~1.5 to 1.2 Ga from the Beidajian Formation of the Ruyang Group in north China (Meng et al., 2005) and from ~1.4-billion-year-old shales of Roper Group from the McArthur Basin, northern Australia (Moldowan et al., 1996(Moldowan et al., , 2001. Dinosteranes, and thus evidence for dinoflagellates, have been reported as free hydrocarbons from the 1.1-bilion-yearold Nonesuch Formation, USA (Pratt et al., 1991), and are commonly found in Neoproterozoic rock extracts, such as from the Officer (Zang and McKirdy, 1993) and Amadeus basins (Summons, 1992) in Australia. Other distinctive C 30 sterane structures found in the Proterozoic rock record include 24-n-propylcholestanes, which are reliable markers for marine pelagophyte algae and appear to be ubiquitous in restricted or open marine depositional settings (Moldowan et al., 1990). ...
... Ga, Roper Group) and the oldest detection of unambiguously syngenetic eukaryotic steranes (ca. 0.75 Ga, Chuar Group) our knowledge is currently limited to only a handful of biomarker studies that targeted rocks at 1.10 Ga (Oronto Group, USA; Imbus et al., 1988;Pratt et al., 1991), 1.11 Ga (Atar Group, Mauretania; Blumenberg et al., 2012) and 1.43 Ga (Roper Group, Australia; Dutkiewicz et al., 2003). The relevance of every additional study contributing to our understanding of Earth system evolution at this period in Earth history is thus incontestable. ...
... Due to the enhanced preservation of organic matter on clay mineral surfaces and their low permeability to migrating fluids, black shales have been considered to be a prime target for Precambrian biomarker research (Summons et al., 1988a,b;Pratt et al., 1991;Brocks et al., 2005;Eigenbrode et al., 2008;Waldbauer et al., 2009;Blumenberg et al., 2012). For example, Brocks et al. (2005) found abundant hydrocarbon biomarkers derived from green sulfur bacteria, purple sulfur bacteria and aerobic methane oxidizing bacteria in black shales of the $1.64-Ga-old Barney Creek Formation in northern Australia, whose molecular inventory has been widely accepted as containing the oldest convincing indigenous biomarkers. ...
... Additionally, most of the samples contain a third, uncommon series of putatively rearranged hopanes-albeit in much lower concentration-characterized by a similar chromatographic distribution pattern to that of hopanes and diahopanes (Fig. 3). Diahopanes have been reported in a large variety of sedimentary rock types from different time periods (Pratt et al., 1991;Telnaes et al., 1992;Farrimond et al., 1998;Zhu et al., 2007;Dutta et al., 2013), including in high abundances in Precambrian sediments (e.g., Summons et al., 1988a,b;Blumenberg et al., 2012). Yet to date, the origin of diahopanes remains unresolved (Dutkiewicz et al., 2003;Smith and Bend, 2004;Zhu et al., 2007). ...
The composition of microbial communities and their relationship to ocean redox structure in the Precambrian are topics of continuing interest in geobiology. Our knowledge of organismic diversity and environmental conditions during this time are mostly based on fragmentary paleontological and geochemical records and might be skewed accordingly. In North China the Xiamaling Formation (∼1.37 Ga) is characterized by black shales of relatively low thermal maturity (Tmax is ∼445 °C) and has been identified as a potential petroleum source rock. To date, however, the biological sources of the organic matter and the environmental conditions prevalent during the deposition of these sediments remain unclear. In this study we analyzed the hydrocarbon biomarker compositions of the Xiamaling Formation shales and a superjacent stromatolitic carbonate in order to shed light on the microbial diversity in the sedimentary environments they represent. The hydrocarbons extracted from both sediments are dominated by low-molecular-weight n-alkanes with a maximum at C15–18, suggesting that bacteria and/or algae were primary biotic precursors. Our inability to detect steranes in bitumen I, and only traces of rearranged steranes in bitumen II of black shales, indicates that modern eukaryotic algae were either ecologically insignificant or not preserved due to a taphonomic bias. The high relative concentration of hopanes and diahopanes ranging from C27 to C35, as well as monomethylalkanes, suggests that cyanobacteria may have been the dominant primary producers and could have contributed to the biologically available nitrogen pool through N2-fixation. This observation is supported by the low nitrogen isotopic composition of the kerogens. Even though all facies zones appear to have been anoxic but not sulfidic on the basis of biomarker ratios and trace metals, subtle but distinct molecular differences are observed between the stromatolite and the black shales, which can be attributed to both, lithologically-controlled diagenetic rearrangements and differential biotic input. The discrepancy between the presence of a large UCM and high abundances of alkyl lipids on one hand, yet the absence of a stable carbon isotopic offset between lipids and kerogen, on the other, suggests that strong heterotrophic reworking might not be the sole source of the biodegraded fingerprint that is so typical for Proterozoic bitumens, and demands alternative explanations.
... 1100 Ma intracratonic Midcontinent Rift System of central North America (Ojakangas et al., 2001). Like the Torridon Group of northwest Scotland, the Nonesuch Formation contains a rich record of eukaryotic life (Pratt et al., 1991; Strother and Wellman, 2010 ) and thus represents an ideal locality to assess possible links to early terrestrial oxygenation. We utilize Fe-S-C systematics to assess water column redox conditions , coupled with Re-Os geochronology to provide a depositional age for the Nonesuch Formation , and Os isotope systematics to yield an insight into the nature of the depositional setting. ...
... An existing U-Pb zircon age of 1087.2 ± 1.6 Ma from the fi nal andesite fl ow in the Copper Harbor Conglomerate (Davis and Paces, 1990) (Fig. 1 ) provides a maximum age for the Nonesuch Formation. To allow redox assessment using Fe-S-C systematics, we sampled well-preserved drill core (PI-1) across a 60 m interval that covers the entire Nonesuch Formation (Pratt et al., 1991). These samples are augmented by Re-Os geochronology and Os isotope analyses of outcrop samples collected ~30 m above the Copper Harbor Conglomerate (Fig. 1; full details of the sampling and analytical protocols are provided in the GSA Data Repository 1 ). ...
... Sedimentological characteristics of the Nonesuch Formation and proximity to continental red beds (Fig. 1), coupled with paleogeographic reconstructions suggesting that the nearest coastline was ~800 km away, indicate that the Nonesuch Formation was likely deposited in a lacustrine environment (Elmore et al., 1989; Imbus et al., 1992; Ojakangas et al., 2001). However, a marine embayment or estuarine environment has also been suggested based on the presence of specifi c biomarkers and S/C ratios (Pratt et al., 1991; Hieshima and Pratt, 1991). Biomarkers extracted from the Nonesuch Formation include low levels of 24-n-propylcholestane (Pratt et al., 1991), which is commonly, but not uniquely, *E-mail: v.m.cumming@durham.ac.uk. ...
A significant body of evidence suggests that the marine environment remained largely anoxic throughout most of the Precambrian. In contrast, the oxygenation history of terrestrial aquatic environments has received little attention, despite the significance of such settings for early eukaryote evolution. To address this, we provide here a geochemical and isotopic assessment of sediments from the late Mesoproterozoic Nonesuch Formation of central North America. We utilize rhenium-osmium (Re-Os) geochronology to yield a depositional age of 1078 ± 24 Ma, while Os isotope compositions support existing evidence for a lacustrine setting. Fe-S-C systematics suggest that the Nonesuch Formation was deposited from an anoxic Fe-rich (ferruginous) water column. Thus, similar to the marine realm, anoxia persisted in terrestrial aquatic environments in the Middle to Late Proterozoic, but sulfidic water column conditions were not ubiquitous. Our data suggest that oxygenation of the terrestrial realm was not pervasive at this time and may not have preceded oxygenation of the marine environment, signifying a major requirement for further investigation of links between the oxygenation state of terrestrial aquatic environments and eukaryote evolution.
... Subsequently, liquid petroleum and reduced water were released from portions of the Nonesuch Formation (e.g., Pratt et al., 1991) located deeper in the basin in response to increased burial and thermal maturation of kerogen. These reduced fluids migrated into the upper Copper Harbor Formation at White Pine, emplacing liquid petroleum and causing selective dissolution of hematite rims and incorporation of Fe into neoformed chlorite or hematite destruction (i.e., bleaching of sandstones and conglomerates). ...
... The first mechanism must certainly have played a role based on the abundant evidence of seawater, which includes evaporite pseudomorphs (Figs. 3D, 9M), sedimentary gypsum beds with marine-like sulfur isotope compositions , marine sedimentary bedforms , and marine organic geochemistry markers Pratt et al., 1991). However, we cannot exclude the possibility that rock buffering influenced δ 18 OFluid, especially given the evidence for detrital grain dissolution documented in this study. ...
White Pine, located in Michigan’s Upper Peninsula, is an archetypal sediment-hosted stratiform copper deposit. The Midcontinent rift system is one of only seven basins globally that host a giant sediment-hosted stratiform copper deposit. Despite many similarities with other deposits of this type, White Pine displays some important differences, including the late Mesoproterozoic age, a thick basalt sequence, an apparent lack of evaporites, and a lacustrine depositional setting. This study analyzes paleofluid flow related to the formation of White Pine and places a particular emphasis on structural and diagenetic fluid pathways.
Most of the ore is located in a 30-m-wide zone spanning the Copper Harbor Formation red beds and the overlying Nonesuch Formation shales. Sedimentation of these units was accompanied by subtle synsedimentary faulting. Premineralization phases include calcite concretions and nodules, illite and hematite grain coatings, isopachous chlorite rims, emplacement of liquid petroleum (now pyrobitumen), and bleaching. Mineralization introduced native copper into the footwall sandstones and a zoned suite of native copper and sulfur-poor copper sulfide minerals across a migrating redox front in the overlying shales where copper minerals nucleated on authigenic and detrital chlorite grains. Postmineralization phases include quartz cement, calcite cement, and calcite veins that partially overlapped inversion of synsedimentary faults. Contrary to previous studies, we identified evidence for only one phase of mineralization. An Re-Os chalcocite age of 1067 ± 11 Ma places mineralization 11 to 17 m.y. after host-rock deposition. Sulfide δ34S values of –14.0 to 29.9‰ suggest an important contribution from sour gas and thermochemical sulfate reduction of seawater. Carbon (δ13C) and oxygen (δ18O) isotope compositions of five calcite generations range from –15.1 to –1.3‰ and 10.4 to 41.3‰, respectively, and record early meteoric pore water displaced by later seawater.
White Pine is both a sediment-hosted stratiform copper deposit and a paleo-oil field. Synsedimentary faults controlled the sedimentological character of the upper Copper Harbor Formation, and together these imparted a strong control on fluid flow and later diagenetic processes. Early oxidized meteoric fluids were displaced by liquid petroleum and sour gas, which were in turn succeeded by metal-rich but sulfate-poor oxidized seawater. Burial compaction during deposition of the overlying Freda Formation drove fluids through White Pine due to its situation on a paleotopographic high near the basin margin. Mineralization occurred at ~125°C at depths of ~2.0 km and spanned incipient basin inversion related to the distal effects of Grenvillian orogenesis. The hightenor copper mineral assemblage is the product of an abundant supply of metal from basaltic volcanic detritus in the Copper Harbor Formation and low seawater sulfate concentrations in late Mesoproterozoic oceans. This demonstrates that viable sediment-hosted stratiform copper systems can form when a readily leachable metal source rock is present, even if hypersaline and sulfate-rich brines are not.
... The rapid process of rifting and resultant regional compression means that rift sediments ( Figure 1) were shallowly buried and minimally heated in some parts of the rift (<125°C; Mauk and Hieshima, 1992). This is due to the absence of large regional tectonic deformation in the mid-continent and the relatively short duration of rifting (Pratt et al., 1991;Price et al., 1996). The MCR experienced prehnite-pumpellyite grade metamorphism in places close to the basin-bounding faults, but thermal history models of available temperature constraints from the Nonesuch and CHC formations within the MCR indicate both low peak burial temperatures and a relatively short duration of burial before unroofing (Gallagher et al., 2017). ...
... Clumped isotope temperatures therefore likely show minor thermal alteration during shallow burial heating since the Mesoproterozoic. Biomarker and clay mineral thermometry support low regional MCR burial temperatures (100-125 °C) (Nishioka et al., 1984;Pratt et al., 1991), but far warmer than measured mat Δ47 values. Regional temperatures from clay and biomarker data are consistent with recent clumped isotope results from the MCR White Pine Mine, that show spatially variable hydrothermal temperatures (49-116°C) in association with zones of copper mineralization, and fluid inclusions show equilibration temperatures of 53-88°C (Nishioka et al. 1984). ...
Palaeoclimate data indicate that Earth surface temperatures have remained largely temperate for the past 3.5 Byr despite significantly lower solar luminosity over this time relative to the present‐day. There is evidence for episodic early and late Proterozoic glaciation, but little evidence of glaciation in the intervening billion years. A prolonged equable Mesoproterozoic Earth requires elevated greenhouse gas concentrations. Two end‐member scenarios have been proposed for maintaining global warmth. These include extremely high pCO2 or more modest pCO2 with higher methane concentrations. This paper reports on the δ13C of organic matter in 1.1 Ga stromatolites from the Copper Harbor Conglomerate (CHC) of the Mesoproterozoic Midcontinent Rift (N. America) and δ18O and Δ47 temperatures of inorganic stromatolite carbonate to constrain formation and burial conditions and the magnitude of ancient carbon isotope discrimination. CHC sediments have never been heated above ~125–155°C, providing a novel geochemical archive of the ancient environment. Stromatolite Δ47 data record moderate alteration and therefore the occluded organic matter was unlikely to have experienced significant thermal alteration after deposition. The δ13C values of ancient mat organic matter and inorganic carbonate show isotope discrimination (εp) values ~15.5 to 18.5‰, similar to modern microbial mats formed in equilibrium with low concentrations of dissolved inorganic carbon. In combination, these data are consistent with a temperate climate Mesoproterozoic biosphere supported by relatively modest pCO2. This result agrees with Atmosphere‐Ocean Global Circulation Model reconstructions for Mesoproterozoic climate using 5–10 times present atmospheric levels pCO2 and pCH4 of >28 ppmv. However, given marine modelling constraints of CH4 production that suggest pCH4 was below 10 ppm, this creates a methane paradox. Either an additional source of CH4 (e.g. from terrestrial ecosystems) or another greenhouse gas, such as N2O, would have been necessary to maintain equable conditions in the Mesoproterozoic. This article is protected by copyright. All rights reserved.
... 1.1 Ga lacustrine Nonesuch Formation, USA, is an additional example of a ferruginous water body based on extensive Fe-C-S systematics (Cumming et al., 2013). Aryl isoprenoids are also below detection limits in the Nonesuch Formation (Imbus, Engel, Elmore, & Zumberge, 1988;Pratt et al., 1991), strengthening the argument against PZE, although the absence of these hydrocarbons may also be due to other factors including thermal destruction. In addition, a persistently oxic water column in the 1.4 Ga Kaltasy Formation in the Ural Mountains, central Russia has been identified based on iron speciation (Sperling et al., 2014). ...
... m in the Altree 2 drillcore. Triangles represent n-alkanes, Pr: pristane; Ph: phytane; UCM: unresolved complex mixture; Neryuen Formation of the Sette-Daban fold belt, Siberia, the 1.1 Ga Nonesuch Formation of the Mid Continent Rift System, North America and deep sections of the 1.64 Ga Barney Creek Formation of the McArthur Group(Pawlowska et al., 2013;Pratt, Summons, & Hieshima, 1991;Summons et al., 1988).Saturated carotenoids, including β-carotene, and associated carotane cleavage products were not detected in the m/z 125-123 chromatogram in any of the extracts in this study based on comparison of elution positions with the Barey Creek Formation(Lee & Brocks, 2011). ...
The ca. 1.38 billion years (Ga) old Roper Group of the McArthur Basin, northern Australia, is one of the most extensive Proterozoic hydrocarbon‐bearing units. Organic‐rich black siltstones from the Velkerri Formation were deposited in a deep‐water sequence and were analysed to determine their organic geochemical (biomarker) signatures, which were used to interpret the microbial diversity and palaeoenvironment of the Roper Seaway. The indigenous hydrocarbon biomarker assemblages describe a water column dominated by bacteria with large‐scale heterotrophic reworking of the organic matter in the water column or bottom sediment. Possible evidence for microbial reworking includes a large unresolved complex mixture (UCM), high ratios of mid‐chained and terminally branched monomethyl alkanes relative to n‐alkanes—features characteristic of indigenous Proterozoic bitumen. Steranes, biomarkers for single‐celled and multicellular eukaryotes, were below detection limits in all extracts analysed, despite eukaryotic microfossils having been previously identified in the Roper Group, albeit largely in organically lean shallower water facies. These data suggest that eukaryotes, while present in the Roper Seaway, were ecologically restricted and contributed little to export production. The 2,3,4‐ and 2,3,6‐trimethyl aryl isoprenoids (TMAI) were absent or in very low concentration in the Velkerri Formation. The low abundance is primary and not caused by thermal destruction. The combination of increased dibenzothiophene in the Amungee Member of the Velkerri Formation and trace metal redox geochemistry suggests that degradation of carotenoids occurred during intermittent oxygen exposure at the sediment–water interface and/or the water column was rarely euxinic in the photic zone and likely only transiently euxinic at depth. A comparison of this work with recently published biomarker and trace elemental studies from other mid‐Proterozoic basins demonstrates that microbial environments, water column geochemistry and basin redox were heterogeneous.
... Precambrian black-shale strata are known in sedimentary basins of Europe, Asia, Africa, Australia, and North America (Bazhenova and Arefiev, 1997;Blumenberg et al., 2012;Donnelly and Crick, 1988;Flannery and George, 2014;Grosjean et al., 2009;Kontorovich et al., 1995Kontorovich et al., , 1999Luo et al., 2015;Peters and Moldowan, 1993;Ponomareva and Sobolev, 2013;Pratt et al., 1991;Summons et al., 1988;Timoshina, 2004Timoshina, , 2005. Study of their organic matter (OM) is aimed at the solution of the problems of the biosphere origin and evolution and the geology and geochemistry of ancient caustobiolith fields. ...
... Ga. However, they were identified in the OM of the Nonesach Formation (1.1 Ga) in North America (US) (Pratt et al., 1991) and in the OM from the Riphean and Vendian rocks of sedimentary basins in the East European Platform (Russia) (Bazhenova and Arefiev, 1997). Analysis of data on the Precambrian sedimentary complexes of Asia, Africa, America, and Australia (Table 3), earlier data on the geochemical composition of Proterozoic biomarkers, and results of molecular dating and study of the origin of eukaryotes (Berney and Pawlowski, 2006;Summons and Walter, 1990) shows that the age of the oldest steroids in black shales and eukaryotic microfossils in rocks is 1.1 Ga. ...
Organic matter (OM) and rocks of the upper member of the Mesoproterozoic Malgin Formation in the southeastern Siberian Platform have been studied by modern research methods. Analysis has revealed homologous series of alkanes, tricyclanes, and hopanes in the bitumens. Leiosphaeridia crassa, L. minutissima, cf. Leiosphaeridia tenuissima, cf. Glomovertella, and Oscillatoriopsis sp. have been identified among the rare microfossils preserved in mudstones. Geochemical, lithological, and paleontological studies have shown that bacterial microcommunities and, to a lesser extent, eukaryotic microorganisms were the main source of OM. Based on results of sedimentological analysis and study of biomarkers, the depositional environment has been reconstructed. A model for the accumulation of black shales and carbonate rocks of the Malgin Formation is considered. The hypothesis that the highly carbonaceous rocks formed in uncompensated depressions of shallow epicontinental marine suboxidation environments is substantiated. The petroleum potential and degree of OM catagenesis of the Malgin Formation rocks are evaluated. Pyrolysis, bitumen analysis, and hydrocarbon composition study have revealed autochthonous and parautochthonous bitumens in the oil shales, mudstones, and carbonate rocks. The obtained data show that the Malgin Formation rocks might have participated in petroleum generation in the Uchur-Maya region.
... The Mesoproterozoic Nonesuch Formation (c. 1.05 Ga) of central North America contains oil seeps within the White Pine copper deposit, Michigan, USA (Imbus et al. 1988;Pratt et al. 1991;Mauk & Hieshima 1992;Price et al. 1996). The source of the eastern Siberian Precambrian oils is also believed to be organic-rich shales of Mesoproterozoic (Riphean) age (Ulmishek 2001). ...
... These shales contain up to 3.0% TOC and are marginally mature to mature with respect to the zone of oil generation. Petroleum seeps and shows from the White Pine mine have been typed to the Nonesuch Formation (Pratt et al. 1991;Mauk & Hieshima 1992). The Neoproterozoic Chuar Group of the eastern Grand Canyon, Arizona, contains the organically richest, thermally mature source rocks with TOC contents of up to 10%. ...
... There are other signs of microbial activity in the Midcontinent Rift System during the Mesoproterozoic as well. The Nonesuch Shale, which directly overlies and interfingers with the Copper Harbor Conglomerate, contains abundant organic carbon and microfossils (Elmore et al., 1989;Pratt et al., 1991;Wellman and Strother, 2015). Additionally, paleosols containing organic matter have been described within interflow deposits of the Portage Lake Lava Series, which interfingers with the Copper Harbor Conglomerate Sheldon, 2009, 2010;Sheldon, 2012). ...
... Although some authors (e.g. Hieshima and Pratt, 1991;Pratt et al., 1991) have argued for a marine influence in the Nonesuch Shale based on S/C ratios and biomarkers, most studies have interpreted it as a lacustrine environment based on facies analyses and paleogeographic reconstructions (e.g. Cumming et al., 2013;Elmore et al., 1989;Imbus et al., 1992;Ojakangas et al., 2001). ...
Stromatolites can form from either biogenic or abiogenic accretionary processes. Mesoproterozoic (1.1 Ga) carbonate stromatolites from the nonmarine Copper Harbor Conglomerate in the upper peninsula of Michigan have been described as biogenic although they lack internal microfossil evidence and exhibit a problematic radial-fibrous calcite that may indicate direct abiogenic precipitation. If shown to be biogenic, they will represent one of the earliest examples of terrestrial microbial activity. Therefore, it is important to determine the biogenicity of these stromatolites and refine a methodology for testing stromatolite biogenicity in the absence of microfossil evidence. Stromatolite samples were collected from four localities within the formation that represent abandoned fluvial channels within an alluvial fan system. The stromatolites are often found in thin (< 0.5 m) oolitic grainstone beds that drape clastic cobbles. They are also found in mudstone lenses that display soft-sediment deformational structures. These stromatolites contain mudstone laminations and are found draping shale rip-up clasts. One method of determining biogenicity of the stromatolites will be to measure growth angles of cobble-draping stromatolites to determine if a preferential growth direction towards sunlight occurred. A new biosignature method using magnetic susceptibility will also be used to test the biogenicity of these stromatolites. The magnetic susceptibility is based on the distribution of detrital material across single laminae. The theory behind this methodology is that biogenic stromatolites are better at trapping sediment (including magnetic minerals) than abiogenic stromatolites because of the adhesive nature of microbial mats. Petryshyn et al. (2011) found support for this in both laboratory experiments and the measured susceptibility in ancient stromatolites. If the susceptibility is similar regardless of growth angle then the hypothesis that the Copper Harbor stromatolites are biogenic will be supported. If the susceptibility varies with different growth angles then the hypothesis that the stromatolites are biogenic will not be supported. The results of this study will have important implications for interpreting the early history of life on Earth, particularly in terrestrial settings.
... There are other signs of microbial activity in the Midcontinent Rift System during the Mesoproterozoic as well. The Nonesuch Shale, which directly overlies and interfingers with the Copper Harbor Conglomerate, contains abundant organic carbon and microfossils (Elmore et al., 1989;Pratt et al., 1991;Wellman and Strother, 2015). Additionally, paleosols containing organic matter have been described within interflow deposits of the Portage Lake Lava Series, which interfingers with the Copper Harbor Conglomerate Sheldon, 2009, 2010;Sheldon, 2012). ...
... Although some authors (e.g. Hieshima and Pratt, 1991;Pratt et al., 1991) have argued for a marine influence in the Nonesuch Shale based on S/C ratios and biomarkers, most studies have interpreted it as a lacustrine environment based on facies analyses and paleogeographic reconstructions (e.g. Cumming et al., 2013;Elmore et al., 1989;Imbus et al., 1992;Ojakangas et al., 2001). ...
... They found no evidence of metasomatic alteration but instead found multiple episodes of weathering and diagenesis. This result is strongly supported by the presence of authigenic smectite in the Oronto Group (Fig. 2; McDowell 1993, Li et al. 1995), indicating only moderate temperatures of diagenesis (,2008 C), the limited thermal maturity (heating ,1258 C) of organic matter in the Nonesuch Formation (Price et al. 1996), and the preservation of biomarkers in the Nonesuch Formation (Pratt et al. 1991) consistent with bacterial sulfate reduction (Hieshima and Pratt 1991) in a standing water body. ...
... As noted already, rift-related basins on both flanks of the MCR contain a combination of volcanic and detrital sedimentary material. The sedimentary units were deposited in a range of terrestrial environments from fluvial channels (Fig. 3B) to paleosols (Zbinden et al. 1988; Mitchell and Sheldon 2009, 2010) to paludal (Mitchell and Sheldon 2009) and lacustrine (Pratt et al. 1991, Price et al. 1996) settings. At Good Harbor Bay (Fig. 1), Mitchell and identified seven paleosols that represent three distinct pedofacies: (1) gleyed floodplain proximal paleosols (Fig. 3E), (2) dry floodplain distal paleosols, and (3) cumulative fluvial floodplain proximal paleosols. ...
... The impetus for the search of oil and gas in this Precambrian rift setting was spurred on not only by the identification of an organic-rich source rock (Nonesuch Fm.) and its associated indigenous live crude oil seeps (Pratt and others, 1991) but also by the attraction of large petroleum reserves in other rift basins of the world (for example, North Sea, Gulf of Suez, and Pripyat Basin) and the proven production of giant petroleum reserves in other Precambrian terranes, such as Lena-Tunguska Petroleum Province, Eastern ...
... It is the finely laminated silty to calcareous shale that contains the highest proportion of organic matter, as high as nearly 3.0 percent TOC (avg. ~0.6 percent) (Imbus and others, 1990; Pratt and others, 1991). The source rock is characterized chiefly by type II and type I kerogens and is moderately mature (T max , 435-440¡C). ...
INTRODUCTION The Superior Province includes all of the State of Minnesota, except for 14 counties in the southeastern corner, the western counties of Wisconsin, and the western Upper Peninsula of Michigan. The 14 southeastern Minnesota counties are included in the Iowa shelf Province. The Superior Province comprises approximately 132,000 sq mi. In northern and central Minnesota, surface bedrock is Precambrian rocks of the Canadian shield, whereas in southern Minnesota, surface bedrock consists of younger (<570 MYBP) Paleozoic and Cretaceous age sedimentary rocks. In northern Wisconsin, Precambrian rocks of the Wisconsin Dome are the surface rocks, whereas in the southwestern part of the State, Cambrian and Ordovician rocks make up the bedrock. Essentially most of the bedrock in the Superior Province is now covered by unconsolidated glacial and postglacial debris. One notable exception is in the Driftless Area in the southwestern part of Wisconsin. No commercial oil has been found in the Superior Province. However, one hypothetical conventional play was identified and individually assessed—the Precambrian Midcontinent Rift System Play (5101). Although parts of the play extend southwest into six other provinces, the play is discussed here (including assessment of its undiscovered resources) because a significant portion of the play lies within the Superior Province.
... Early work from the Nonesuch Formation putatively identified steranes, biomarkers indicative of eukaryotes (Pratt et al., 1991), but recent analyses suggest this was due to contamination, and any steranes present are below detection limits (Brocks et al., 2008;Brocks, 2018). This result contrasts with microfossil identifications of eukaryotes and suggests three options: (a) eukaryotes are in low absolute abundance compared to prokaryotes in the lake (in contrast to the richness and abundance data of organic-walled microfossil species; Fig. S13) and a minor component of primary productivity, (b) steranes were not preserved in the samples targeted for biomarker analyses (e.g., Cohen and Kodner, 2022), or (c) the eukaryotic microfossils did not produce sterane precursors (sterols) and were thus stem-group organisms (e.g., Porter, 2020). ...
The Nonesuch Formation microbiota provide a window into ca. 1075 Ma life within the interior of ancient North America. The Nonesuch water body formed following the cessation of widespread volcanism within the Midcontinent Rift as the basin continued to subside. In northern Michigan and Wisconsin, USA, the Copper Harbor Conglomerate records terrestrial alluvial fan and fluvial plain environments that transitioned into subaqueous lacustrine deposition of the Nonesuch Formation. These units thin toward a paleotopographic high associated with the Brownstone Falls angular unconformity. Due to these “Brownstone Highlands,” we were able to explore the paleoenvironment laterally at different depths in contemporaneous deposits. Rock magnetic data constrain that when the lake was shallow, it was oxygenated as evidenced by an oxidized mineral assemblage. Oxygen levels were lower at greater depth—in the deepest portions of the water body, anoxic conditions are recorded. An intermediate facies in depth and redox between these endmembers preserves detrital magnetite and hematite, which can be present in high abundance due to the proximal volcanic highlands. This magnetic facies enabled the development of a paleomagnetic pole based on both detrital magnetite and hematite that constrains the paleolatitude of the lake to 7.1 ± 2.8°N. Sediments of the intermediate facies preserve exquisite organic-walled microfossils, with microfossils being less diverse to absent in the anoxic facies where amorphous organic matter is more likely to be preserved. The assemblage of cyanobacteria and eukaryotes (both photoautotrophs and heterotrophs) lived within the oxygenated waters of this tropical Mesoproterozoic water body.
... Neither of these possible routes for 3methyl diasterane generation from kerogen is likely to be quantitatively significant, but could be consistent with the typically low levels of 3methyl-24-ethyl diasteranes reported in normal solvent extracts (e.g. Pratt et al., 1991;Grosjean et al., 2012). Limited potential for 3-methyl diasteroid formation in extractable bitumen during diagenesis is suggested by the restriction of methyl diaster-13 (17)-enes to the 4-methyl series in the relatively few examples of m/z 271 mass chromatograms of immature bitumen available in the literature (e.g. ...
The potential origin of 3-methyl steroids is investigated through comparison of their carbon number distributions with those of their desmethyl counterparts using GC–MS and GC–MS-MS analysis of a range of oils and some immature source rock bitumens. There is a close genetic link between desmethyl and 3-methyl steranes, consistent with competition between methylation and hydrogenation at C-3 in the shared steroidal precursors, producing strongly positively correlated carbon number distributions within the two series. The absence (or possibly very low levels) of detectable 3-methyl diasteroids in immature bitumen samples suggests that these compounds are not formed in the free bitumen during diagenesis in amounts capable of explaining their abundance in oils. It is possible that they are produced by a limited degree of rearrangement of steroids after they are bound into kerogen or upon cleavage from kerogen and methylation during catagenesis. Support for this proposition is provided by the previous detection of desmethyl diasterenes in the hydropyrolysate of pre-extracted algal biopolymers, as well as the high diasterane/sterane ratios reported in several studies of hydrous pyrolysis of kerogen. Competition between methylation and hydrogenation during catagenetic formation of diasteranes might explain the lower diasterane/regular sterane ratio observed for 3-methyl compared to desmethyl species.
... Although extractable steranes have been previously reported from mature 1.7-1.3 Ga P a l e o p r o t e r o z o i c a n d M e s o p r o t e r o z o i c successions from the Yanshan Basin in North China (e.g., Li et al., 2003) and from the 1.1 Ga Nonesuch Formation, USA (Pratt et al., 1991), t h e s e s i g n a l s l i k e l y r e c o r d l a t e -s t a g e contamination by anthropogenic fossil fuel sources. Recent reanalysis of putative Archean steranes and hopanes from the Pilbara Craton, Australia (French et al., 2015), and even analysis of thermally well-preserved and organic-rich Proterozoic strata of the 1.64 Ga Barney Creek Formation, Australia , and the 1100 Ma Touirist Formation of Mauritania (Blumenberg et al., 2012), indicate that steranes in these successions are below detection limits and suggest that prior to the Neoproterozoic (>1 Ga), the absolute abundance of eukaryotes was low. ...
The transition to the diverse and complex biosphere of the Ediacaran and early Paleozoic is the culmination of a complex history of tectonic, climate, and geochemical development. Although much of this rise occurred in the middle and late intervals of the Neoproterozoic Era (1000–541 million years ago [Ma]), the foundation for many of these developments was laid much earlier, during the latest Mesoproterozic Stenian Period (1200–1000 Ma) and early Neoproterozoic Tonian Period (1000–720 Ma). Concurrent with the development of complex ecosystems, changes in the composition, configuration, and tectonic interaction between continental plates have been proposed as major shapers of both climate and biogeochemical cycling, but there is little support in the geologic record for overriding tectonic controls. Biogeochemical evidence, however, suggests that an expansion of marine oxygen concentrations may have stabilized nutrient cycles and created more stable environmental conditions under which complex, eukaryotic life could gain a foothold and flourish. The interaction of tectonic, biogeochemical, and climate processes, as described in this paper, resulted in the establishment of habitable environments that fostered the Ediacaran and early Phanerozoic radiations of animal life and the emergence of complex, modern-style ecosystems.
... The Nonesuch Shale of Michigan has 0.25 to 2.8 weight percent present day 1 TOC (averaging 0.6%) and a generally low to moderate thermal history with respect to oil generation (correlated vitrinite reflectance (Ro) between 0.65% and 1.0% (Hieshima et al., 1989;McMahan and Kneller, 1986). Active seeps geochemically associated with this unit are present in northern Michigan (Mauk and Hieshima, 1992;Pratt et al., 1991). To-date, no commercial oil and gas production has been established from the Midcontinent rift. ...
... Previous studies have suggested that in the case of dominant C 27 and C 28 regular cholestane, the parent material is mainly low-grade aquatic organisms such as algae. In the case of higher contents of C 29 , the parent material is terrestrial higher plants, and yet a large number studies have also confirmed that lower aquatic organisms such as algae are also one of main sources for C29 sterane (Czochanska et al. 1988;Pratt, Summons, and Hieshima 1991;Hackley et al. 2013). The content of C 27 , C 28 and C 29 regular cholestane of samples from the Wutonggou Formation in study area is of 18.96 $ 24.49%, 32.12 $ 36.81% and 40.62 $ 44.23%, with averages of 23.18%, 34.43% and 42.39%, respectively. ...
Total organic carbon content (TOC), carbon isotope and biomarker analysis have been done on the source rocks from Lucaogou and Wutonggou formations in Junggar Basin, NW China. (1) the TOC values of the source rocks are more than 5%, and the kerogen types are type I1-II, and the organic matters are mainly algae and bacteria, and are in the mature stage. (2) the depositional environments of the source rocks are weak reduction-weak oxidation, and are of weakly salty water to brackish water environment.
... Variations in sterane carbon number distributions with respect to geological time were well-known for oils derived from marine source rocks [9]. Many published monographs of 3-methylesterases are typically linked to occurrences in oils and source rocks of Palaeozoicfacies and older age [10,11,12,13,14]. The ratio of dibenzothiophene and phenanthrene (DBT/P) recommended as an indicator of the availability of low sulfur for incorporation into organic matter and therefore is a valuable carbonate/shale facies discriminator [15]. ...
This present paper includes a detailed evaluation of specific biomarkers together with stable carbon
isotope (δ13C) by gas chromatography-mass spectrometry (GC–MS) and Gas Chromatograph–
Isotope Ratio Mass Spectrometry (GC–IR–MS). Eight crude oil samples were collected from the A,
B, H (east) and H (west) Fields, located in the Murzuq Basin, Libya. Stable Carbon isotope data
(δ13C) together with biomarker ratios data of individual hydrocarbons, n-alkanes, isoprenoids,
terpenes, hopanes, steranes and aromatic have been determined in crude oils to delineate their
bacterial degradation, source facies, organic matter precursors, depositional conditions and a
variation of maturation. Based on source-specific parameters including n-C19 alkane, % C27S,
%C28S, %C29S, %C23TT, %C30αβ, %rC28, DBT/P, CPI, Pr/Ph, Ts/Tm, dh 30/h 30, 1 MN, 2 MN,
26-27 DMN, 15 DMN, 236 TMN, 146-135 TMN, 125 TMN, 136 TMN ratios and δ13C‰ of saturates
and aromatics fractions. Such oils showed non-biodegradation, n-C19 peak proved oils generated
from a Lower Palaeozoic source rocks as emphasizedvian-C19 peak, the dominance of over C27 and C28 with light Carbon isotope ratio (δ13C‰) values. The abundances of isosterane C29,
C27, C28.Tricyclohexaprenol and bacteriohopane polyols and aminopolyols, recommended as
mixture bioprecursors of tricyclic terpenes and hopanes, furthermore regular sterane ratio gives
values characteristic of Lower Palaeozoic marine source rocks and holding green algae and most
likely a quantity of contribution from acritarchs. Carbon preference indices (CPIs)>0.9 pointed to an
anoxic deposition, dibenzothiophene to phenanthrene (DBT/Prange 0.49 - 0.58) recommend a
siliciclastic source rather than carbonate and/or evaporate saline deposition. The ratios of CPIs,
pristane/n-C17 and phytane/n-C18, n-alkanes (C16 to C22) against (C23 to C33), Ts/Tm,
C30diahopane/C30hopane, methylnaphthalene, dimethyl naphthalene and trimethyl naphthalene
indicated that the oils analysed are mature except the B Field oil being slightly less mature than the
A, H (east) and H (west) Fields oils.
... Variations in sterane carbon number distributions with respect to geological time were well-known for oils derived from marine source rocks [9]. Many published monographs of 3-methylesterases are typically linked to occurrences in oils and source rocks of Palaeozoicfacies and older age [10,11,12,13,14]. The ratio of dibenzothiophene and phenanthrene (DBT/P) recommended as an indicator of the availability of low sulfur for incorporation into organic matter and therefore is a valuable carbonate/shale facies discriminator [15]. ...
This present paper includes a detailed evaluation of specific biomarkers together with stable carbon isotope (δ13C) by gas chromatography-mass spectrometry (GC–MS) and Gas Chromatograph–Isotope Ratio Mass Spectrometry (GC–IR–MS). Eight crude oil samples were collected from the A, B, H (east) and H (west) Fields, located in the Murzuq Basin, Libya. Stable Carbon isotope data (δ13C) together with biomarker ratios data of individual hydrocarbons, n-alkanes, isoprenoids, terpenes, hopanes, steranes and aromatic have been determined in crude oils to delineate their bacterial degradation, source facies, organic matter precursors, depositional conditions and a variation of maturation. Based on source-specific parameters including n-C19 alkane, % C27S, %C28S, %C29S, %C23TT, %C30αβ, %rC28, DBT/P, CPI, Pr/Ph, Ts/Tm, dh 30/h 30, 1 MN, 2 MN, 26-27 DMN, 15 DMN, 236 TMN, 146-135 TMN, 125 TMN, 136 TMN ratios and δ13C‰ of saturates and aromatics fractions. Such oils showed non-biodegradation, n-C19 peak proved oils generated from a Lower Palaeozoic source rocks as emphasizedvian-C19 peak, the dominance of C29steranes over C27 and C28 with light Carbon isotope ratio (δ13C‰) values. The abundances of isosterane C29, C27, C28.Tricyclohexaprenol and bacteriohopane polyols and aminopolyols, recommended as mixture bioprecursors of tricyclic terpenes and hopanes, furthermore regular sterane ratio gives values characteristic of Lower Palaeozoic marine source rocks and holding green algae and most likely a quantity of contribution from acritarchs. Carbon preference indices (CPIs)>0.9 pointed to an anoxic deposition, dibenzothiophene to phenanthrene (DBT/Prange 0.49 - 0.58) recommend a siliciclastic source rather than carbonate and/or evaporate saline deposition. The ratios of CPIs, pristane/n-C17 and phytane/n-C18, n-alkanes (C16 to C22) against (C23 to C33), Ts/Tm, C30diahopane/C30hopane, methylnaphthalene, dimethyl naphthalene and trimethyl naphthalene indicated that the oils analysed are mature except the B Field oil being slightly less mature than the A, H (east) and H (west) Fields oils.
... The specimens from these localities are indeed L. ternata, but because the species is evidently marine and derives from successions that are certainly marine in all cited references (see 'Occurrence'), its occurrence in different environments in Scotland and USA is puzzling. It is suggested that the intervals containing L. ternata represent marine ingressions, as was previously inferred for both succession intervals (Downie 1973;Pratt et al. 1991; but see Strother & Wellman 2016). ...
The diversification of protists and multicellular microorganisms is recorded in numerous worldwide Tonian age successions, including the Visingsö Group in Sweden. The Visingsö Group contains a taxonomically rich assemblage of cyanobacteria, stromatolites, algal phytoplankton and vase-shaped microfossils. A new record of organic-walled microfossils from the Visingsö 1 drillcore reveals the high taxonomic diversity. Several species are reported for the first time from the Visingsö Group, and one new species Leiosphaeridia gorda n. sp. is described. They are in gross phycoma-like cysts of the prasinophycean algae Pterospermopsimorpha, Pterospermella, Simia, Macroptycha and Dictyotidium. Morphologically similar to zygotic cysts of chlorophycean algae are Leiosphaeridia gorda n. sp., Cerebrosphaera, Culcitulisphaera and Lanulatisphaera. Schizofusa may represent the earliest yellow-green algae of the Eustigmatiphyte among Stramenopiles. The recorded biodiversity documents the global trend in the evolution of eukaryotic protists during the Tonian Period and the increased radiation of numerous, presumably photoautotrophic biotas, representing various algal lineages.
... Likewise, the relationships between the Cercozoa and other eukaryotic groups are not well resolved, although most place the Cercozoa well within the crown of the eukaryotic tree (e.g., Philippe and Adoutte, 1995;Cavalier-Smith and Chao, 1996/7;Medlin et al., 1997;Bolivar et al., 2001). Thus, until better resolution is attained, Melicerion poikilon indicates only that the eukaryotic crown group had begun to diversify by ϳ750 Ma, consistent with evidence from a growing number of Late Mesoproterozoic/Early Neoproterozoic eukaryotic crown group fossils (e.g., Summons et al., 1988;German, 1990;Pratt et al., 1991;Butterfield et al., 1994;Woods et al., 1998;Butterfield, 2000). ...
Vase-shaped microfossil (VSM) assemblages from early diagenetic carbonate nodules in >742 ± 6 Ma black shales of the Chuar Group, Grand Canyon, provide evidence for affinities with testate amoebae. Not only are VSMs exceptionally preserved in Chuar rocks, they exhibit a much higher degree of morphological diversity than was previously known. Using the taxonomy of modern testate amoebae as a guide, nine new species and eight new genera of VSMs are described, augmenting the eight species and two genera already recognized. Taxa described here are Melanocyrillium hexodiadema Bloeser, 1985, Trigonocyrillium horodyskii (Bloeser, 1985) n. comb., T. fimbriatum (Bloeser, 1985) n. comb., Cycliocyrillium simplex n. sp., C. torquata n. sp., Bonniea dacruchares n. sp., B. pytinaia n. sp., Trachycyrillium pudens n. sp., Palaeoarcella athanata n. sp., Hemisphaeriella ornata n. sp., Bombycion micron n. sp., and Melicerion poikilon n. sp. All of the test characters observed in VSM taxa (e.g., collars; indentations; hexagonal symmetry; lobed, triangular or invaginated apertures; curved necks) occur in modern testate amoeban taxa, though not always in the same combinations. Some VSM species have characters found today in diverse extant taxa, making it difficult to assess their relationships. A few species, however, have character combinations that closely approximate those found in specific genera of both lobose and filose testate amoebae, suggesting that at least stem group, and possibly crown group, representatives of these taxa were present ∼742 Ma.
These fossils indicate that ecosystems were diverse and complex, that eukaryotic biomineralization had already evolved, and that the last common ancestor of animals+fungi had already appeared by ∼750 Ma.
... The earliest such derivatives have been reported from sediments 1.1-1.2 Ga in age (Pratt et al. 1991;Meng et al. 2005), suggesting this to be the minimum age for the origin of dinoflagellates and thus creating a very large discrepancy with the palynological record with respect to the first occurrence of the dinoflagellates. Hopefully, further work on both morphology (and perhaps genetics) of unassigned morphotypes and geochemical analyses will continue to decrease this age gap. ...
... Although extractable steranes have been previously reported from mature 1.7-1.3 Ga P a l e o p r o t e r o z o i c a n d M e s o p r o t e r o z o i c successions from the Yanshan Basin in North China (e.g., Li et al., 2003) and from the 1.1 Ga Nonesuch Formation, USA (Pratt et al., 1991), t h e s e s i g n a l s l i k e l y r e c o r d l a t e -s t a g e contamination by anthropogenic fossil fuel sources. Recent reanalysis of putative Archean steranes and hopanes from the Pilbara Craton, Australia (French et al., 2015), and even analysis of thermally well-preserved and organic-rich Proterozoic strata of the 1.64 Ga Barney Creek Formation, Australia , and the 1100 Ma Touirist Formation of Mauritania (Blumenberg et al., 2012), indicate that steranes in these successions are below detection limits and suggest that prior to the Neoproterozoic (>1 Ga), the absolute abundance of eukaryotes was low. ...
... The mmb-alkanes were once referred as "X-peaks" (Klomp, 1986), and later identified as co-eluting mixtures of midchain monomethyl branched alkanes (Fowler and Douglas, 1987;Summons and Powell, 1992). The mmbalkanes (usually with even-over-odd predominance in >C 20 homologues at low maturity) are a common feature of Proterozoic organic matter (Klomp, 1986;Fowler and Douglas, 1987;Shiea et al., 1990;Pratt et al., 1991;Hayes et al., 1992;Summons, 1992;Summons and Powell, 1992;Logan et al., 1999). Phanerozoic occurrences of such compounds are much more limited, with reports confined mainly to extant microbial mats from hypersaline and hydrothermal environments (Robinson and Eglinton, 1990;Kenig et al., 1995). ...
The Wuliu-Zengjiayan section in Jianhe County, Guizhou Province, China has been suggested as a potential Global Stratotype Section and Point (GSSP) for the defined base of Cambrian Series 3. A molecular organic geochemical study on the Cambrian Series 2-Series 3 boundary interval was carried out to reveal the biotic and environmental change during this transition. The hydrocarbons extracted from the Kaili Formation were proved to be indigenous. The various geochemical proxies such as biomarker parameter, δ 13Corg, atomic H/C value of kerogen, and TOC content, co-vary along with the sedimentary column, and show a quick and significant change just across the Cambrian Series 2-Series 3 boundary. The less abundance of isoprenoid hydrocarbons, the relative enrichment of midchain monomethyl branched alkanes (mmb-alkanes), the relatively negative value of δ 13Corg, and the higher TOC contents may suggest that the upper Cambrian Series 2 was deposited in a relatively reducing environment with a higher organic input from cyanobacteria-predominated benthic microbial mats. On the other hand, the relative enrichment of isoprenoid hydrocarbons, the less abundance of mmb-alkanes, the relatively positive value of δ 13Corg, the lower TOC contents, and the lower atomic H/C values of kerogen are combined to indicate an enhanced phytoplankton production and an increased oxygen content and nutrients in the ocean during the early Cambrian Series 3, which could have benefited the explosion of the Kaili Biota. The Wuliu-Zengjiayan section may provide a typical case to understand the co-variation of marine microbe, animal, and environment.
... В экспериментах 1, 3-5 в биодеградированных пробах I 3 , III 2 , IV 2 , V 2 по сравнению с исходными пробами I 1 , III 1 , IV 1 , V 1 существенно возросла концентрация метилтриароматических стероидов и диностеранов (биометки динофлагелят) [Pratt et al., 1991;Summons, Walter, 1990] (рис. 4.50). ...
В монографии рассмотрены общие проблемы защиты окружающей среды (почв, грунтов и вод) от опасных и устойчивых к разложению химических веществ и приведены результаты собственных исследований, направленных на разработку химических, в частности, каталитических и сорбционных методов обезвреживания опасных химических веществ (гептил, полихлорированные углеводороды, тяжелые металлы), микробиологических и интегрированных методов ремедиации нефтезагрязненных природных сред. Рассмотрены вопросы эффективного контроля очистки методом биологического тестирования, а также геохимическими методами по результатам изучения избирательности и стадийности процессов трансформации нефтяных УВ.
Для научных работников, преподавателей вузов, аспирантов, студентов, специализирующихся в области экологической химии, геохимии и микробиологии, решающих задачи охраны окружающей среды, устойчивого развития и рационального природопользования.
... A simplified correlative stratigraphic section on the south shore and north shore is given in Fig. 2. Syn-rift paleosols have been documented on both sides of the MRS, in Minnesota (Mitchell and Sheldon, 2009) and Michigan (Kalliokoski, 1975;Kalliokoski and Welch, 1985;Zbinden et al., 1988;Mitchell and Sheldon, 2010). While many Precambrian paleosols show evidence of significant burial alteration (e.g., Maynard, 1992), previous mass balance calculations (Mitchell and Sheldon, 2009) authigenic smectite (Li et al., 1995), low organic matter maturity (Price et al., 1996), and biomarker preservation (Pratt et al., 1991) all indicate minimal metasomatism or metamorphism of the MRS rocks following formation, in part because many parts of the MRS were never significantly buried (Ojakangas et al., 2001). Results presented herein will include paleosols from MRS sites in Minnesota at Good Harbor Bay and Temperance River State Park (Fig. 1). ...
Based upon various proxy, theoretical, and model constraints, Paleoproterozoic atmospheric pCO(2) was much higher than Phanerozoic levels. However, relatively little is known about the transition between the two climate states. Here, geochemicalmass-balance from similar to 1.1 Ga old Midcontinent Rift System(USA) paleosols is used to reconstruct atmospheric pCO(2) during the Mesoproterozoic. The calculations robustly indicate low atmospheric pCO(2) (<10 times Preindustrial levels). Results are consistent between seven paleosols at one site, between paleosols at different Midcontinental Rift sites, and between the new results and previously published penecontemporaneous paleosol and microfossil reconstructions. The newly recognized Mesoproterozoic pCO(2) minimum is best explained as the culmination of a long-term C burial event by the biosphere that is also indicated by marine carbonate delta C-13 changes during the Mesoproterozoic, and which is consistent with changes in the biosphere including increased stromatolite abundance and diversity, evolution of sulfur-utilizing bacteria, and the spread of microbial mats into continental environments.
... numerous workers (Imbus et al., 1988(Imbus et al., , 1992Elmore et al., 1989;Ho et al., 1990;Pratt et al., 1991;Strauss et al., 1992), allowing for estimated reconstruction of originally buried organic carbon values. Corrections using kerogen elemental data providing an H/C ratio of 0.53 and an equation 3.2.2 for fractional carbon loss (Strauss et al., 1992) on the dominant organic-rich facies containing Type I kerogen with an assumed original H/C ratio of 1.6 (Imbus et al., 1988(Imbus et al., , 1992 suggest an organic carbon loss of around 43%. Thus the TOC values of the Nonesuch Shale can be regarded as representing only about 60% of the originally buried organic carbon (Table 1). ...
... The earliest such derivatives have been reported from sediments 1.1-1.2 Ga in age (Pratt et al. 1991;Meng et al. 2005), suggesting this to be the minimum age for the origin of dinoflagellates and thus creating a very large discrepancy with the palynological record with respect to the first occurrence of the dinoflagellates. Hopefully, further work on both morphology (and perhaps genetics) of unassigned morphotypes and geochemical analyses will continue to decrease this age gap. ...
Within dinoflagellate research the fields of geology and biology come together in studies of the resting stage, the cyst. Studies of this stage and life-cycle transitions can tie together the geological fossil record of dinoflagellates and the ecology of living dinoflagellates. This review focuses on possible new research areas within ploidy shifts in dinoflagellate life cycles, the role of the cyst in benthic-pelagic coupling, the cyst as the link between the past and present, the role of cysts in long-term survival and preservation of cysts and cyst-wall chemistry.
... Isotopic values were calculated for benthic and pelagic sources using equations 1 and 2 defined in the text. organic matter (Klomp, 1986;Fowler and Douglas, 1987;Pratt et al., 1991;Summons and Powell, 1992;Hayes et al., 1992;Logan et al., 1997), but their origin is still controversial. In other Proterozoic bitumens, from Oman and Siberia, mid-chain methyl alkanes have been reported to extend out past C 30 (Klomp, 1986;Fowler and Douglas, 1987). ...
A combined sedimentological and biogeochemical study has been conducted on several Terminal Proterozoic mid-shelf microbial mat facies from the Centralian Super-basin. Isotopic and organic geochemical analysis of the bitumen and kerogen indicated that two sources of organic matter from 'planktonic' and 'benthic microbial-mat' populations contributed to the sediment. The 'planktonic' source provided a suite of n-alkanes with C 20 predominance and the odd n-alkanes C 20 , whereas, the 'benthic' source contributed an overlay of n-alkanes C 20 with a strong even preference, together with mid-chain methyl alkanes. Kerogen and biomarkers derived from the microbial mat were found to be depleted in 13 C relative to planktonic material. Pyrite in the micorbial mats was also found to be depleted in 34 S compared to surrounding facies. The combination of these observations suggested that the mats may have been at least partly composed of sulfide oxidising bacteria. These organisms have specific environmental tolerances that set limits on palaeo-environment. Their requirement for oxygen indicates that the water column above the mid-shelf could not have been anoxic. Accordingly, from the results and age determinations reported here, it would appear that mid-shelf environments of the Centralian Superbasin of Australia were seeing significant levels of oxygen through the Ediacarian.
Different opinions on the oil-source correlation and migration of the Moxizhuang-Yongjin block in the Junggar Basin, NW China, have seriously affected oil and gas exploration in this area. This research is based on the results of biomarker analysis and carbon isotope of monomer hydrocarbon on crude oil and source rock samples from different blocks. Two oil families (A1, A2, and B) are classified by cluster analysis on nine typical biomarker ratios. Typically, sub-family A1 oils are distributed in the Zhuang 102 well block of the Moxizhuang block, and their gammacerane index is the highest. The abundance of C24 tetracyclic terpanes is the lowest, the C27 regular steranes are dominant, and the organic matter is mainly input by lower aquatic organisms. Sub-family A2 oils are distributed in the Zheng 1-1 well block of the Moxizhuang block. The gammacerane index of oils is lower than the former, and the abundance of C24 tetracyclic terpanes is higher. In the dual input of lower aquatic organisms and terrestrial higher plants, the input of terrestrial higher plants accounted for a larger proportion. Family B oils are distributed in the Yong 2 well block of the Yongjin block, and their gammacerane index is the lowest. They have a high abundance of C24 tetracyclic terpanes, and C29 regular steranes are dominant, reflecting the characteristics of terrigenous organic matter contribution. Based on the biomarker compound composition, at least two oil charges are indicated: Sub-family A1 oils are likely sourced from the Wuerhe formation, sub-family A2 oils may be a mixture of Wuerhe formation and Badaowan formation, and family B oils are likely sourced from the Badaowan formation. The oil families with typical genetic affinities may indicate two major petroleum systems or multiple oil systems existing in the study area. In addition, the characteristics of hydrocarbon accumulation and migration are also discussed, the oil and gas in the West Sag of Well Pen 1 and Changji Sag are filled from deep to shallow in the vertical direction and migrated from south to north in the horizontal direction, at the same time, with the help of sand bodies and faults, and they migrated to the north and northeast. This work provides a scientific basis for oil and gas exploration in the hinterland of the Junggar Basin.
Precambrian source beds have been discovered worldwide. The sedimentary ages of these strata are mainly 2.7–2.6 Ga, ca. 2.0 Ga, 1.6–1.4 Ga, ca. 1.0 Ga, 0.7–0.6 Ga, and 0.6–0.5 Ga respectively. The characteristics of these source beds are closely related to the evolution of microbe, from aquatic cyanobacteria to eukaryotes as well as the preservation conditions for organic matter. The occurrence and thriving of eukaryotic algae in ecosystems may increase the possibility of oil-prone source bed formation. Geological processes, including crustal weathering, volcanic activity and glaciations, are also essential for the development of large-scale source beds. Thermal degradation of organic matter has been regarded as one of the most important factors controlling Precambrian source bed quality, and thus detailed and precise research on maturity would be very important for the evaluation of oil and gas potential. As macro fossils are rare in Precambrian source beds, the biomarkers, i.e., molecular fossils, present powerful tools for tracing the Precambrian microbial communities. For example, based on some specific biomarkers, the first appearance of sulfate-reducing bacteria and green sulfur bacteria can be dated to 1.64 Ga. The diversity of biomarkers in Precambrian strata provides a basis for oil-source rock correlation. For example, the source beds of bituminous sandstones in the Xiamaling Formation as well as oils in Oman have been successfully confirmed using both the specific biomarkers, 13α(n-methyl)-tricyclic terpanes and C19 A-norsterane. The researchers also reveal that carbon isotopic composition of organic matter in Precambrian strata remarkably differs from those in the Phanerozoic. Although the tremendous progress has been made in the discovery of Precambrian biomarkers, trace amounts of those compounds in the strata also provoked the debate regarding the indigeneity of Precambrian organic matter. Nevertheless, it is believed that this problem can be solved as analytical technology progresses in the future.
Since 1960s, the significant research progress on the Proterozoic early lives and life diversity as well as on the Meso-Neoproterozoic shales and carbonate source rocks have established a material foundation for the studies of indigenous Meso-Neoproterozoic sedimentary organic matter and petroliferous nature, and providing the prerequisites for the prospectivity of indigenous petroleum resources. So far at least dozens oil and gas fields, some of considerables size, have been discovered in the Meso-Neoproterozoic strata, oil and/or gas of which were sourced from the Infracambrian source beds. Based on uncompleted global statistics, there are four countries, i.e., Lena-Tounguska Petroleum Province (LTPP) in Siberia Craton (Russia), Oman Basins in Arabian Craton (Oman), Baghewala Oilfield in Indian Craton (India), and Anyue Gasfield in western Yangtze Craton (China), in the world, containing proven geological reserves and/or commercial production of indigenous Infracambrian petroleum; nine regions/countries having been confirmed indigenous Meso-Neoproterozoic oil flow, oil-seep and/or asphalt, but so far no commercial production has been obtained yet; five regions/countries being revealed to possess hydrocarbon generation potential in the Infracambrian strata. China is one of the countries where the Meso-Neoproterozoic sequences are most completely developed and preserved, and Chinese Meso-Neoproterozoic geology was earlier studied in the word. However, both geological research and exploration of Meso-Neoproterozoic petroleum resources are faced with a challenging reality of more age-old strata, more complicated geological tectonics and more extensive scientific innovative possibility. Therefore, it is a considerable urgent question to study and evaluate the prospectivity of Meso-Neoproterozoic oil and gas resources in China. In this chapter, the distribution, exploration and development of Meso-Neoproterozoic oil and gas respectively in Russian LTPP, Sultanate of Oman, Pakistan and India basins, East European Craton, African Taoudenni Basin, Australian Centralian Basins, American Midcontinent Rift System as well as Chinese basins have been compiled, and their prospectivity approached.KeywordsMeso-neoproterozoicLena-tounguska petroleum province (LTPP)Anyue gasfieldOman basinsYanliao faulted-depression zone (YLFDZ)
During the deposition of the Chang 7 Member of the Yanchang Formation, pronounced lake invasion occurred, resulting in the formation of the largest lake in the Ordos Basin. This change has caused ambiguity in the source rock characteristics among the different sedimentary environments represented, thereby restricting the exploration of oil–source correlations and hydrocarbon migration pathways corresponding to oil and gas in this formation. In this study, we comprehensively assessed the characteristics of source rocks from different sedimentary environments and selected effective biomarker parameters to allow for a detailed exploration of oil formation and hydrocarbon migration. The source rock biomarkers differed notably among the different sedimentary environment, with source rocks from semi-deep to deep lakes having high ratios of pristane to phytane and ∑C21-/∑C22+ n-alkanes, relatively high C27 regular sterane contents, and low (C19+C20)/C21 and C30-rearranged hopane contents. Source rocks from these facies developed in reductive environments and had high V/Cr, Ni/Co, V/(V+Ni), and U/Th values, while those from the delta facies developed in a semi-oxidative to oxidative environment and thus showed the opposite characteristics. The Chang 6 tight oil in the Dingbian-Wuqi area primarily migrated vertically near its source; the western block originated from semi-deep to deep lake source rocks, while the eastern block formed from delta front source rocks. These findings should guide future research in this reservoir, especially with respect to high-resolution oil–source correlations across different sedimentary environments.
Continental paleoclimate records provide a means to assess regional climate variability through time and assess how the evolution of the terrestrial biosphere has driven and responded to environmental change. Fossil soils (paleosols) are a particularly useful paleoclimate archive, because they are widely distributed throughout the geologic record. Carbonate clumped isotope paleothermometry is an exciting new proxy for paleosols, as it has the potential to assess temperature seasonality. Yet the processes underlying soil carbonate formation and clumped isotope temperature resetting must be further understood before this proxy can be effectively applied. My dissertation centers on improving understanding of the processes controlling soil carbonate formation and critically evaluating the potential resetting of clumped isotope carbonate data from terrestrial deposits. In Chapter 2, I use modern samples to explore seasonal biases associated with the clumped isotope composition of soil carbonate. The results demonstrate that soil carbonate can form at or below mean annual temperatures. The cold nature of these results is explained by the annual timing of soil water depletion, which is driven by patterns of seasonal precipitation and evapotranspiration. In Chapter 3, modern soil environmental data are compiled to examine how soil temperatures relate to surface air temperatures and to quantify systematic biases that will affect paleosol proxies. Seasonal fluctuations in soil moisture are used to predict the seasonal timing of pedogenic carbonate formation. Soil temperature data indicate that pedogenic carbonate is more likely to record warm season bias relative to mean annual air temperature. In Chapter 4, I use clumped isotope and organic biomarker analyses on the 1.1 Ga Nonesuch Formation to explore how easily the clumped isotope thermometer can be reset on geologic samples and to evaluate the performance of new solid-state reordering models. Using a solid-state reordering model, I illustrate that the synsedimentary and early-diagenetic calcite were partially reset to elevated temperatures. Taken together, these results illustrate factors that must be considered when producing environmental reconstructions from pedogenic carbonate and other terrestrial archives. These findings provide guidance on how to extract accurate paleoclimate information from paleosol carbonate and highlight the need for a process-based understanding of pedogenic carbonate formation.
Mesoproterozoic marine organic-rich rocks are widely distributed in the North China Craton, include the Gaoyuzhuang (GYZ), the Hongshuizhuang (HSZ), and the Xiamaling (XML) formations. According to the Tmax value and isomerisation ratio of C31 homohopanes, the XML, HSZ, and GYZ samples were in low mature, mature and high mature stage, respectively. Biomarker distribution in extractable organic matter (EOM) of three Mesoproterozoic organic-rock samples in different maturity were analysed to reveal the organic precursor and preservation pathway of in the Mesoproterozoic Combined with gold-tube pyrolysates of three Mesoproterozoic samples, it could further illuminate the chemical composition of Mesoproterozoic kerogen, given excluding. The results indicated that the three formations were all deposited under reducing condition and their organic precursors mainly were some aquatic organisms. High content of rearranged hopanes was detected in EOM of XML and HSZ samples, whereas they were relatively low in the high mature GYZ sample. Contrast to that in EOM, the relative concentration of rearranged hopanes sharply decreased in the gold-tube pyrolysates of the XML kerogen, then slightly increased but was still significantly lower than the EOM of XML sample, which indicated that catalysis of clay minerals in the early diagenesis only changed the chemical composition of the unstable functional groups of the kerogen during the preservation. Due to the thriving heterotrophic microbes and low sink rate of particulate organic matter during the Mesoproterozoic, primary producers suffered extensive degradation during sinking process, only some resistant biopolymers lacking of lipid compounds survived from heterotrophic degradation, while heterotrophic microbes contained more proportion of organic precursors. Abundant pristane (Pr) and phytane (Ph) were only released in high mature stage because of the protection of the macromolecular structure of resistant biopolymers which prevented biomarkers from being altered by the thermal stress. The absence of 13α(n-alkyl)-tricyclic terpanes in the high matured hydrocarbon products also indicated the different precursors between different parts of Mesoproterozoic kerogen. The evolution of the biomarker composition and content of Mesoproterozoic kerogen showed some special characteristics differing from those of Phanerozoic kerogen. The total concentrations of hopanes displayed with an order of low mature stage > high mature stage > mature stage. Relative content of rearranged hopanes in the hydrocarbon generated in high mature stage was significantly lower than that in the low maturity stage. The ratios of Pr/n-C17 and Ph/n-C18 increased with thermal maturity, and the ratio of nC21-/nC22+ decreased in the high maturity stage, thus displaying another order of mature stage > high maturity stage > low maturity stage. The unique preservation pathway of Mesoproterozoic organisms was attributed to the special evolution characteristics of biomarker distributions, which should be considered in the Mesoproterozoic marine environment and biological studies.
Lakes are important archives for continental records of paleoenvironmental as well as paleoclimatic change. They also record a unique macroevolutionary pattern that occurred when faunas invaded the continental realm. In order to document that pattern, we compiled a database of over ninety lake basins from the Neoproterozoic to the Permian. Each basin was evaluated based upon its sedimentology and paleontology and, where appropriate, was classified into one of three types: underfilled, balanced-filled, and overfilled, sensu Carroll and Bohacs (1999). The faunal elements from each were recorded at the species, generic, class, and phylum levels.
Looking at this critical time in lacustrine evolution, several patterns emerged. For the Neoproterozoic through Silurian time, there is a paucity of documented lake deposits and lake faunal records. Lakes during this time were oligotrophic and their nutrient cycling regimes were primitive. It is not until the establishment of land plants in the Silurian that lakes begin to respond with higher diversities and more complex physical and chemical conditions. During the Devonian-Carboniferous periods, diversity was on the rise as trophic levels became more complex. Globally, CO2 increased while marine Sr decreased, coinciding with the peaking of diversity within lakes. Most lakes of the Devonian and Carboniferous formed along continental margins or in tectonic basins with occasional connection to the marine realm. The faunas from these types of lakes were commonly comprised of mixed marine and freshwater elements and were far more diverse than other, more inland lakes. This “estuary effect” created a gateway or filter through which faunas invaded the continental realm.
The early history of lake faunas is one of opportunity and amelioration. The feedback loops created by the establishment of vascular plants altered the nutrient cycle on land and in lakes. All trophic levels were established early but became increasingly complex throughout the Paleozoic, as roles changed and faunal elements became established. Groups invading the continents via the “estuary effect” did so numerous times before establishing themselves permanently. This was linked with the episodic reestablishment in marine-freshwater connections along these continental margins. In general, the macroevolutionary history of lake faunas demonstrates a dramatically different diversification pattern than that of the marine, and further study is necessary to understand the intricacies of these patterns and whether or not they continue through the Mesozoic and Cenozoic eras.
The 1.1 Ga Midcontinent Rift (MCR) is a thick volcanic-sedimentary succession that forms a curvilinear belt through central North America and crops out along its northern apex around Lake Superior. Sedimentary units of the MCR have been long interpreted as fluvial-lacustrine and invited a number of studies on the early evolution of life in non-marine habitats. One of the key units is the siliciclastic Nonesuch Formation, thought to record deposition in a large lake. However, recent sedimentological observations indicate the presence of marine incursions. To further test this interpretation, we analyse trace element abundances in a broad suite of samples from multiple drill cores through the Nonesuch Formation. We aim to differentiate geochemical influences of sediment provenance from post-depositional hydrothermal overprint and thereby identify authigenic enrichments in fluid-mobile elements that are indicators of primary environmental conditions. Our results reveal discrete enrichments in Mo and U in organic- and sulphide-rich horizons, which are most parsimoniously interpreted as marine signatures. This conclusion is supported by Sr/Ba ratios, which suggest mixing between freshwater and saltwater, and by rare cm-thick gypsum in the upper Copper Harbor Formation immediately below the Nonesuch rocks. The gypsum displays δ³⁴S values of +25.9 ± 0.6‰, consistent with input of marine sulphate at least during parts of the basin's history. Collectively, our geochemical data support the sedimentological observations that this portion of the MCR archives a marine-influenced estuarine system. Although this rules out exclusively freshwater habitats, the Nonesuch and associated rocks hold important clues about organisms that were capable of withstanding salinity gradients and bridges the gap between the marine and non-marine environments of the mid-Proterozoic.
The c. 1.1 Ga Copper Harbor and Nonesuch Formations of the Keweenawan Supergroup exposed along the Canadian-United States shorelines of Lake Superior are part of the surface exposures of the Laurentian Midcontinent Rift. These units have long been considered non-marine in origin and have figured prominently in ideas regarding the evolution of microbial life and the redox conditions of Earth’s ocean-atmosphere system at the close of Mesoproterozoic time. However, these rocks also host hydrothermal metal deposits, the emplacement of which may have compromised primary geochemical signals that are used to underpin those ideas. Here we highlight new sedimentological observations to provide an independent framework for assessing the depositional setting and geochemistry of those strata. We show that the totality of sedimentological features leads to the conclusion that parts of the upper Copper Harbor Formation and the entirety of the Nonesuch Formation were deposited along tide- and wave-influenced shorelines and in shallow-marine settings under evaporitic conditions. Evidence for this interpretation includes the abundance of flaser, wavy, linsen and pinstripe bedding, ubiquity of reactivation surfaces and mud drapes associated with all ripple forms, superposed sets of ripple cross-lamination showing bimodal (herring-bone) sediment transport directions, desiccation cracks and metre-scale hummocky cross-stratification. Further, evaporite fabrics and pseudomorphs after gypsum in the upper 200 m of the Copper Harbor Formation and in numerous stratigraphic positions within the Nonesuch Formation indicate that the water body was saline, not fresh. The emerging palaeogeographic image is one of a large, shallow-marine embayment with fringing sabkha-like shorelines. Ideas about late Mesoproterozoic biospheric evolution and Earth’s surface redox and oxygenation that rely on the Nonesuch Formation and Copper Harbor stromatolites having been deposited within a lacustrine setting require reassessment.
Terrestrial environments have been suggested as an oxic haven for eukaryotic life and diversification during portions of the Proterozoic Eon when the ocean was dominantly anoxic. However, iron speciation and Fe/Al data from the ca. 1.1-billion-year-old Nonesuch Formation, deposited in a large lake and bearing a diverse assemblage of early eukaryotes, are interpreted to indicate persistently anoxic conditions. To shed light on these distinct hypotheses, we analyzed two drill cores spanning the transgression into the lake and its subsequent shallowing. While the proportion of highly reactive to total iron (Fe HR /Fe T ) is consistent through the sediments and typically in the range taken to be equivocal between anoxic and oxic conditions, magnetic experiments and petrographic data reveal that iron exists in three distinct mineral assemblages resulting from an oxycline. In the deepest waters, reductive dissolution of iron oxides records an anoxic environment. However, the remainder of the sedimentary succession has iron oxide assemblages indicative of an oxygenated environment. At intermediate water depths, a mixed-phase facies with hematite and magnetite indicates low oxygen conditions. In the shallowest waters of the lake, nearly every iron oxide has been oxidized to its most oxidized form, hematite. Combining magnetics and textural analyses results in a more nuanced understanding of ambiguous geochemical signals and indicates that for much of its temporal duration, and throughout much of its water column, there was oxygen in the waters of Paleolake Nonesuch.
We use core descriptions and portable X-ray fluorescence analyses to identify lithofacies and stratigraphic surfaces for the Mesoproterozoic Nonesuch Formation within the Ashland syncline, Wisconsin. We group lithofacies into facies associations and construct a sequence stratigraphic framework based on lithofacies stacking and stratigraphic surfaces. The fluvial-alluvial facies association (upper Copper Harbor Conglomerate) is overlain across a transgressive surface by the fluctuating-profundal facies association (lower Nonesuch Formation). The fluctuating-profundal facies association comprises a retrogradational sequence set overlain across a maximum flooding surface by an aggradational-progradational sequence set comprising fluctuating-profundal, fluvial-lacustrine, and fluvial-alluvial facies associations (middle Nonesuch through lower Freda Formations). Lithogeochemistry supports sedimentologic and stratigraphic interpretations. Fe/S molar ratios reflect the oxidation state of the lithofacies; values are most depleted above the maximum flooding surface where lithofacies are chemically reduced and are greatest in the chemically oxidized lithofacies. Si/Al and Zr/Al molar ratios reflect the relative abundance of detrital heavy minerals vs. clay minerals; greater values correlate with larger grain size. Vertical facies association stacking records depositional environments that evolved from fluvial and alluvial, to balanced-fill lake, to overfilled lake, and returning to fluvial and alluvial. Elsewhere in the basin, where accommodation was greatest, some volume of fluvial-lacustrine facies is likely present below the transgressive stratigraphic surface. This succession of continental and lake-basin types indicates a predominant tectonic driver of basin evolution. Lithofacies distribution and geochemistry indicate deposition within an asymmetric half-graben bounded on the east by a west-dipping growth fault. While facies assemblages are lacustrine and continental, periodic marine incursions are probable, especially across maximum transgressive surfaces.
Recent decades have witnessed a revolution in our understanding of the geological events and nature of life in Precambrian time. A period of Earth history once described simply as “the Azoic” (e.g., Dana, 1866) is now recognized as an interval of great complexity in terms of biological systems and their influence on the evolution of the hydrosphere and atmosphere. Characterization of Precambrian tectonic processes and climatic regimes, and their consequent sedimentological responses (e.g., transgressive-regressive sequences, glaciation, euxinic oceans), has demonstrated that, as in the Phanerozoic, biological radiations and extinctions probably reflect selective pressures exerted by such events. The evolution of new metabolic pathways and the advent of biogenic sedimentation transformed the character of sedimentary rocks. Accumulation of atmospheric oxygen, often attributed to increased levels of photoautotrophy, led to the deposition of iron formations and redbeds as well as enabling the evolution of later life forms (i.e., eukaryotic algae, metazoans, and metaphytes), with their profound sedimentological influences.
A new chroococcalean cyanobacterium is described from approximately 1-billion-year-old non-marine deposits of the Torridonian Group of Scotland and the Nonesuch Formation of Michigan, USA. Individual cells of the new microfossil, Eohalothece lacustrina gen. et sp. nov., are associated with benthic microbial biofilms, but the majority of samples are recovered in palynological preparations in the form of large, apparently planktonic colonies, similar to extant species of Microcystis. In the Torridonian, Eohalothece is associated with phosphatic nodules, and we have developed a novel hypothesis linking Eohalothece to phosphate deposition in ancient freshwater settings. Extant cyanobacteria can be prolific producers of extracellular microcystins, which are non-ribosomal polypeptide phosphatase inhibitors. Microcystins may have promoted the retention and concentration of sedimentary organic phosphate prior to mineralization of francolite and nodule formation. This has a further implication that the Torridonian lakes were nitrogen limited as the release of microcystins is enhanced under such conditions today. The abundance and wide distribution of Eohalothece lacustrina attests to the importance of cyanobacteria as oxygen-producing photoautotrophs in lacustrine ecosystems at the time of the Mesoproterozoic-Neoproterozoic transition.
Whole oil gas chromatography shows that petroleum inclusions trapped in 1.05 Ga veins in the Midcontinent rift experienced variable water washing but no significant biodegradation or phase separation. By comparing our results with published experimental data, we estimate that water:petroleum ratios varied from 200:1 to much greater than 9000:1. Extreme water washing with water:petroleum ratios very much greater than 9000:1 likely produced pyrobitumen (solid hydrocarbon) that was locally trapped as primary inclusions in vein calcite. Hydrothermal ore deposits, with their extremely high water:rock ratios, are one of the best places to search for end-member water-washed petroleum. Sedimentary basins, however, with their variable water:rock ratios, also have a wide range of water:petroleum ratios, which significantly affect the composition of crude oils along the flow path between source rock and trap. Water:petroleum ratios may be a useful concept to help evaluate crude oil compositions in a variety of settings.
U.S. Geological Survey Digital Data Series DDS-69-T, Chapter 2, 162p.
Published 2015.
Economic stratiform copper mineralization in the fine-grained, carbonaceous basal Nonesuch Formation of the ∼50-km-wide White Pine-Presque Isle mining district, northern Michigan, has long been explained by the essentially vertical infiltration of cupriferous brine across the full width of basal Nonesuch strata from the underlying Copper Harbor Conglomerate aquifer, followed by copper precipitation mainly by reactions with in situ iron sulfide. Based on that model, why do lesser amounts of total copper, measured in vertical sections, occur in coarser grained (presumably more permeable) basal Nonesuch strata situated laterally to the east and west of the mining district? The answer may lie in increased infiltration rates for Copper Harbor-hosted ore-forming brine warmed locally by latent volcanic heat from a resurgent caldera (or calderas) located within the large Porcupine Volcanics dome underlying the mine district. Not only would caldera heat have warmed the brine and lowered its density, but more importantly it would have produced a remarkable decrease in the brine viscosity. An increase in temperature from 15° to 100°C could have increased the brine infiltration rate by more than four times in very early diagenetic time when the sediments were poorly compacted and highly porous. Because progressive compaction would have opposed the temperature effect, a very early diagenetic timing is suggested for main-stage copper mineralization over the Porcupine Volcanics caldera. Textural evidence has also long supported an early mineralization event. At the rift-basin scale, the exceptionally rapid upward flux of warmed brine into fine-grained Nonesuch over the caldera would have required equivalent volumes of replacement brine, which would in turn have required a lateral convergence of brine within the footwall Copper Harbor Conglomerate aquifer toward the White Pine-Presque Isle district. This lateral focus of brine toward the warm caldera area would have created a more efficient basin-scale ore-forming system than that resulting from a linear hydrogeologic flow. Most concepts described here deserve further evaluation through quantitative hydrogeologic modeling. Thermal effects on ore brine viscosities and densities, developed here for the sediment-hosted stratiform copper mineralization of the White Pine-Presque Isle district, could be considered in genetic models for other deposits and deposit types. The effects are especially strong for solutions warmed from low temperatures (e.g., 20°C or lower) to 100°C, and could also be important to ore fluid flow for ores involving much higher hydrothermal temperatures if solutions with initially low temperatures played a role in their genesis.
This textbook provides a unique and thorough look at the application of chemical biomarkers to aquatic ecosystems. Defining a chemical biomarker as a compound that can be linked to particular sources of organic matter identified in the sediment record, the book indicates that the application of these biomarkers for an understanding of aquatic ecosystems consists of a biogeochemical approach that has been quite successful but underused. This book offers a wide-ranging guide to the broad diversity of these chemical biomarkers, is the first to be structured around the compounds themselves, and examines them in a connected and comprehensive way.This timely book is appropriate for advanced undergraduate and graduate students seeking training in this area; researchers in biochemistry, organic geochemistry, and biogeochemistry; researchers working on aspects of organic cycling in aquatic ecosystems; and paleoceanographers, petroleum geologists, and ecologists.Provides a guide to the broad diversity of chemical biomarkers in aquatic environmentsThe first textbook to be structured around the compounds themselvesDescribes the structure, biochemical synthesis, analysis, and reactivity of each class of biomarkersOffers a selection of relevant applications to aquatic systems, including lakes, rivers, estuaries, oceans, and paleoenvironmentsDemonstrates the utility of using organic molecules as tracers of processes occurring in aquatic ecosystems, both modern and ancient.
Annual Review of Earth and Planetary Sciences http://arjournals.annualreviews.org/loi/earth
The isoprenoid hydrocarbons, phytane (C20H42) and pristane (C19H40), are present in the oil seeping from the Precambrian Nonesuch formation at the White Pine Mine, Michigan. Gas-liquid chromatography
and mass spectrometry provide the isolation and identification procedures.
Precambrian, unmetamorphosed, organic-rich clastic rocks, whilst uncommon in the geologic record, are of interest with respect to their potential for hydrocarbon generation. The ∼ 1.1 billion year old Nonesuch Formation is primarily a lacustrine deposit which is part of a thick sequence of volcanic and clastic sedimentary rocks that filled an aborted rift in central North America. Previous organic geochemical investigations of the Nonesuch Formation have been limited to isolated samples from the basal portion of the Nonesuch Formation at a copper mine (White Pine) in northern Michigan.In the present study, 183 outcrop and core samples of the Nonesuch Formation from northern Wisconsin and Michigan (Upper Peninsula) were collected for sedimentologic and organic geochemical analyses. Total organic carbon (TOC) values for the samples ranged from 0.0 to 2.5% and showed a strong correlation between organic richness and depositional environment. Detailed petrographic analysis using incident white light and reflected blue light fluorescence revealed two major organic petrographies (1 and 2) which could be further distinguished using combined pyrolysis-gas chromatography/mass spectrometry (PY/GC/MS). Whereas the composition of Organic Petrography 1 kerogens is primarily aliphatic, the composition of Organic Petrography 2 kerogens is dominated by aromatic and/or phenolic constituents. The geographic and stratigraphic distribution of rocks bearing the two organic petrographies indicate that variable source-input or preservation, superimposed over maturity differences, is responsible for both organic petrographic and kerogen pyrolysate compositions.
The authors have tested a Rb-Sr technique that permits ore deposits to be dated using common gangue minerals such as calcite and fluorite. The only conditions the deposit must meet are that (1) it have minerals with a low Rb/Sr ratio and (2) it be enclosed by wall rock with a high Rb/Sr ratio. Because hydrothermal minerals acquire a strontium-isotope composition that is usually similar to that of the wall rock, minerals with low Rb/Sr ratio should record and retain the isotopic composition that the wall rock had at the time of mineralization. The difference between that ratio and that of the wall rock at present is a function of time and the Rb/Sr composition of the wall rock. The technique was tested fusing fluorite and calcite from three deposits ranging in age from Tertiary to Precambrian. In all cases the age determined here closely resembles that obtained by conventional K-Ar and Rb-Sr dating methods. The precision, however, can be poor and depends chiefly on the strontium-isotope heterogeneity of the wall rock and its Rb/Sr enrichment. 36 references, 1 figure, 1 table.
The Precambrian Nonesuch Formation crops out in northern Wisconsin and Michigan and is recognized as a possible petroleum source rock based on active oil seeps in copper mines of the White Pine area. Sedimentological and organic geochemical analyses of about 200 samples from outcrops, cores, and mine excavation were undertaken to evaluate the petroleum potential of the Nonesuch Formation. Organic carbon (C/sub org/) contents above 0.3% are restricted to thin intervals of finely laminated calcareous and noncalcareous silty shale. C/sub org/ for finely laminated samples ranges from 0.25% to 2.8% and averages 0.6%. Total sulfur (TS) values range from 0.4% to 2.7%. Using samples containing only framboidal pyrite, a positive covariance between C/sub org/ and TS is recognized, with an approximate C/sub org//TS ratio of 0.5. This value is significantly higher than the Goldhaber/Kaplan, Gautier, or Tuttle ratios for Phanerozoic shales. Nonesuch bitumens are alkane rich and depleted in asphaltenes. Gas chromatography of extracts shows a decreasing distribution of alkanes from Cââ to Cââ with a slight enrichment of n-Cââ and n-Cââ. pristane is abundant in several samples, with pristane/n-Cââ ratios approaching 1.0. Pristane/phytane ratios range from 2.5 to 6.0 and average 4.1. Biomarkers suggest that the unit is within the middle part of the oil window. If thicker sections of the organic-rich facies are present in the southern extension of the rift or downdip of the outcrop belt under Lake Michigan, the petroleum source potential of the Nonesuch should be good.
The Nonesuch Formation (ca. 1.1 Ga), host to the White Pine copper deposit, is a generally organic-rich unit of relatively wide extent. Selected strata, away from mineralization, were analyzed for their organic carbon and total sulfur contents and for the amount and composition of extractable organic matter. Sulfur to carbon ratios are covariant, but the ratios of total sulfur to organic carbon are generally higher than those found for marine Phanerozoic black shales deposited under oxic bottom water conditions. The sulfur to carbon ratios and the intimate association fo framboidal pyrite and organic matter are suggested to be the result of bacterial sulfate reduction in the Nonesuch sediments. Activity of sulfate reducing bacteria requires a supply of sulfate in the water column and implies that the depositional environment was not a low-sulfate aqueous environment. A marine embayment dominated more by sea water than riverine input is suggested as the environment of deposition based on the correlation of total sulfur and organic carbon, the relatively high total sulfur content, and on the absence of sedimentologic and geochemical criteria for saline lacustrine environments. Deposition of highly reactive organic matter in low concentrations coupled with high concentrations of reactive iron and the absence of bioturbation resulted in unusually efficient pyrite formation.
Age determinations by the total-rock Rb-Sr method of several suites of felsite from the White Pine area of Michigan indicate
dates ranging from 978 + or - 40 m.y. to 1,100 + or - 25 m.y. A single specimen of felsite from Government Peak of the Porcupine
Mountains was dated at 1,042 + or - 32 m.y. Assuming that the Porcupine Mountains are an anticline, this date sets an upper
limit to the time of deposition of the overlying Nonesuch Shale. Another upper limit is provided by dates of 1,107 and 1,180
m.y. for two felsite pebbles from the lower sandstone unit of the Parting Shale member exposed in the old Nonesuch Mine.Nine
samples of mineralized and unmineralized rock from the basal section of the Nonesuch Shale exposed in the mine workings of
the White Pine Mine were analyzed. These samples form a good co-linear array in coordinates of Rb 87 /Sr 86 and Sr 87 /Sr 86 . The apparent age, calculated from the slope of the isochron, is 1,075 + or - 50 m.y. The initial Sr 87 /Sr 86 ratio is 0.7080 + or - 0.0008. The apparent age of the Nonesuch Shale is interpreted to be slightly greater than the time
of deposition because of the probable incorporation of inherited Sr 87 into the sediment at the time of deposition.The isotope composition of three lead samples extracted from chalcocite of the
ore body at White Pine was found to be anomalous. This suggests that the lead in the ore was mixed with radiogenic lead and
favors an epigenetic or late diagenetic rather than a syngenetic origin for the copper sulfide in the basal portion of the
Nonesuch Shale.
Investigations have been made of crude oil, pristane, phytane, steranetype and optically active alkanes, porphyrins, microfossils,
and the stable isotopes of carbon and of sulfur found in the Nonesuch shale of Precambrian age from Northern Michigan. These
sediments are approximately 1 billion years old. Geologic evidence indicates that they were deposited in a nearshore deltaic
environment. Porphyrins are found in the siltstones but not in the crude oils of the Nonesuch formation—evidence that these
chemical fossils are adsorbed or absorbed and immobile. This immobility makes it highly unlikely that these porphyrins could
have moved from younger formations into the Nonesuch sediments, and the widely disseminated particulate organic matters and
fossils in this Precambrian shale are certainly indigenous.
A series of C13 to C31 aryl isoprenoids (1-alkyl,2,3,6-trimethylbenzenes) have been identified in reef-hosted oils and their source rocks from the Middle and Upper Silurian of the Michigan Basin and Middle Devonian of the Alberta Basin, Canada. Their structure has been confirmed by unambiguous synthesis of the C14 member of the series. Their structure and isotopic composition indicate that they are derived from isorenieratene from the Chlorobiaceae family of sulphur bacteria. These results are consistent with geological and geochemical studies that show that the source rocks were deposited under metahaline to hypersaline sulphate and sulphide rich water columns. The distribution of other biomarkers in these oils and source rocks indicates that a diverse biota contributed organic matter to the source environment. In conjunction with the aryl isoprenoids, they show that there is a remarkable similarity in composition between the two sets of oils and source rocks despite their great temporal and geographic separation. This reflects the similarity of their environments and emphasizes the importance of sedimentary facies in controlling the composition of organic matter in source rocks and their derived oils.
The continental lithosphere which hosts the Midcontinent Rift (MCR) system comprises a crustal assemblage ranging in age from 3.6 to 1.5 Ga. The most voluminous igneous activity along the MCR occurred within Late Archean (2.7 Ga) crust, presumably due to magmatism associated with a rising mantle plume. Two major arms of the rift extend to the southeast and the southwest, where rifting, magmatism, and sedimentation were confined to a 2000 km long rift that cuts through the various crustal provinces ranging in age from 3.6 to 1.5 Ga. Tensional reactivation of pre-existing crustal discontinuities may have influenced the location of parts of the MCR; however, direct cause and effect are difficult to distinguish for want of sufficient exposures.The most active phases of magmatism and rifting occurred between 1109 and 1087 Ma; a U-Pb age of 1097 Ma for the southern end of the MCR shows that magmatic activity was synchronous throughout its length. There is evidence of rifting and magmatism prior to 1109 Ma, but there is little evidence of magmatism after 1087 Ma; rifting may have effectively ceased by that time. Rifting may have ceased as a result of compressional forces being exerted on the foreland during the Grenville collisional event, spanning 1030-970 Ma, and compressional reactivation of normal faults may have resulted in partial inversion of the MCR.Chemical data and U/Pb and Sm/Nd isotopic data for igneous rocks along the rift are similar to those for MCR rocks in the Lake Superior area, which are best explained in terms of a mantle-plume model. However, since the distal arms of the MCR were developed in Proterozoic lithosphere and did not involve nearly as much magmatism as in the Lake Superior area, mantle-plume sources may not have been as important in formation of the distal magmas. Data from the buried arms are also consistent with the mafic magmas being derived by decompression melting of Proterozoic lithosphere during rifting.
Abundant extractable hydrocarbons, in association with well preserved kerogen, have been recognised in a dolostone from the Chuar Group (approx. 850 Ma). The biomarkers present include C15-C30, acyclic isoprenoids, C26-C28 steranes, C27-C35 hopanes and extended tricyclic terpanes. Among the striking characteristics of the distributions are the dominance of steranes and methyl steranes lacking side-chain alkylation and the presence of putative C29-C35 neohopanes and gammacerane. The high abundance of steranes is consistent with the presumed eukaryotic affinities of several types of microfossils, including Chuaria, present in associated mudstones. This stratum is the oldest in which gammacerane has been found, and suggests contributions from protozoa to the depositional environment which appears to have been hypersaline. There is a strong correlation between the carbon isotopic composition of the kerogen and that of the various polarity fractions of the bitumens. Chemical degradation and pyrolysis of the kerogens yielded n-alkanes with similar characteristics to the bitumens, but there are differences in the patterns of distribution of the acyclic isoprenoid, sterane and triterpane biomarkers.
Middle Proterozoic organic-rich sediments from the McArthur Basin in northern Australia contain abundant hydrocarbons which are derived from syngenetic kerogen and hence, are representative of the organic remains of microorganisms living at that time. The major classes of hydrocarbons identified were n-alkanes, monomethyl branched alkanes, cyclohexyl alkanes and acyclic isoprenoids. There were also low abundances of pentacyclic triterpanes comprising hopanes and methyl hopanes. Low concentrations of steranes were present in most samples, but like the triterpanes, they were only easily detected in the least thermally altered sediments, and hence were of limited use in detailed assessments of thermal maturity. The presence of steranes in sediments of this age is strong evidence for the existence of eukaryotic organisms as far back as 1690 Ma, although the relatively high abundances of branched alkanes indicates that most of this primitive organic matter was probably derived from prokaryotes.
Certain C(30)-steranes have been used for identifying sedimentary rocks and crude oils derived from organic matter deposited in marine environments. Analysis of a C(30)-sterane from Prudhoe Bay oil indicates that these C(30)-steranes are 24-n-propylcholestanes that apparently are derived from precursor sterols 24-n-propylidene-cholesterols and 24-n-propylcholesterol. These widely occurring sterols are biochemically synthesized in modern oceans by members of an order (Sarcinochrysidales) of chrysophyte algae. These data thus imply that C(30)-sterane biomarkers in sedimentary rocks and crude oils have a marine origin. Screening of a few organic-rich sedimentary rocks and oils from throughout the Phanerozoic suggests that these C(30)-steranes first appeared and, therefore, their source algae evolved between Early Ordovician and Devonian.
P~eobiol~y of a ~~rnb~an shafe Geochronology of the Ke-weenawan rocks
- E S Mein~hein
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Occurrence of isoprenoid alkanes in a Precambrian sediment In Advances in Organic Geo-chemistry
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Proterozoic Biogeochemistry
- Hayes
Sedimentary 24-n-propylcholestanes, molecular fossils diagnostic of marine algae
- Moldowan